Wednesday, Oct. 4, 2017, a monkey walks over the rubble left in the wake of Hurricane Maria on Cayo Santiago, known as Monkey Island, in Puerto Rico. (Ramon Espinosa/AP)

In the run up to and wake of a natural disaster, there is often lament at the inevitability of the destruction and helplessness of humans in the face of it. Indeed, the word “natural” connotes something not human-made.

With a hurricane, the storm itself often becomes the focus of reporting, but the shape of a natural disaster, and the resultant effect on human life, is largely human-made and not just determined by wind speed or rainfall.

Hurricane Maria laid waste to Puerto Rico nearly four weeks ago, but the disaster has yet to end. Parallels can be drawn between the governmental response to Hurricane Katrina 12 years ago and Hurricane Maria last month. Yet Puerto Rico faces challenges unlike New Orleans 12 years ago, and unlike other similarly impacted areas of the United States.

Unlike New Orleans, and most other parts of the United States subject to the effect of “hurricane alley,” Puerto Rico is tropical. As such, it must contend with diseases that do not pose any or as much of a threat as other areas of the United States. In particular, Dengue fever and Zika virus set Puerto Rico apart from areas of the United States similarly affected by hurricanes this year.

Both diseases are transmitted by mosquitoes, but have very different effects.

Dengue fever can lead to death if left untreated. It is typically not a major problem in Puerto Rico, although epidemics flare up from time to time. Since 1990, there have been five epidemics (1994, 1998, 2007, and 2010) with the epidemic in 2010 being the most widespread, with as many as 26,766 cases.

Zika virus was first detected in Puerto Rico in 2015 and, owing to its symptoms, is more of a concern than Dengue fever. Unlike Dengue fever, a person with Zika virus may not show any symptoms and thus not seek treatment. However, a baby born to an infected mother can suffer severe neurological damage due to microcephaly caused by the virus. This “silent” disease is especially distressing.

In Brazil, studies have shown about eight out of every 100 infants infected with Zika-caused microcephaly die before or shortly after birth. Of those that survive, the prognosis is dire. Neurological disfunction on par with severe cerebral palsy will likely set in within 1-2 years after birth.

The average medical cost for treating a child with microcephaly is estimated to be 3.8 million dollars over the duration of their life, though the cost could reach as much as 10 million dollars. This calculation takes into account that most children who survive the neonatal stage with microcephaly will likely not make it to adulthood.

In 2016 there were between 5,900 and 10,300 possible cases of Zika-infected pregnant women in Puerto Rico. Infection of the mother, even if unknowing, does not always spell microcephaly for the infant. The complexities of how microcephaly develops are still poorly understood and in need of more research. Though with that many possible cases, there would likely be between 100 and 270 infants that develop microcephaly.

Kevin Keegan is a Ph.D. student in the Department of Ecology and Evolutionary Biology at UConn. He studies the systematics and biogeography of moths in the deserts of North America. He can be reached via email kevin.keegan@uconn.edu. He tweets at @MothPotato.